Cochlear implant systems have been developed in order to deliver electrical stimulation directly to the auditory nerve. Such a stimulation bypasses hair cells of the cochlea, which may be damaged or missing in persons who are profoundly deaf, and allows the brain to perceive a sensation resembling the natural hearing sensation normally delivered to the auditory nerve. U.S. Pat. No. 4,532,930, the contents of which are incorporated herein by reference, provides a description of one type of cochlear implant system.
Cochlear implant systems typically comprise two components, firstly an external component commonly referred to as a processor unit, and secondly an implanted component commonly referred to as a stimulator/receiver unit. The external processor unit typically has a microphone for detecting sound, a speech processor for converting the detected sounds into a coded signal, a power source such as a battery, and an external transmitter coil for transmitting the coded signal to the implanted stimulator/receiver unit. The implanted stimulator/receiver unit usually includes a receiver coil for receiving the coded signal from the external transmitter coil, and a stimulator for processing the coded signal and for controlling stimuli applied by an intracochlea electrode assembly.
When a malfunction arises during operation of such systems, it is desirable to provide a non-subjective indication of that malfunction. For instance, where the system is used on a person who has been profoundly deaf since birth, the implant recipient is often unable to provide an accurate indication of whether the implant is operating correctly. Further, where the implant recipient is an infant, the infant is unable to provide any subjective indication of unsatisfactory or faulty operation. Previous systems have monitored battery strength in the external processor unit, however such monitors fail to indicate malfunctions which may arise in the microphone, speech processor, transmitter coil, or implanted stimulator/receiver unit.
A further solution, set out in U.S. Pat. No. 5,941,905, has been to provide a guardian/teacher with a “wand”, comprising an antenna to detect emissions of a recipient's implant, However this arrangement necessitates individually checking each and every implant, which can be a particularly time consuming process where multiple implant recipients are present, and further complicates the already demanding task of teaching or nursing infants. Further, with recent efforts to minimise electromagnetic interference caused by the RF link of such an implant, the performance of such “wands” may become less reliable, as minimal leakage fields may exist for the wand to detect.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.